Transgalactosylation properties of the commercial preparations of beta-galactosidase: Lactase and Maxilact and of the preparation synthesized by Penicillium canescens, were compared.The effect of 2% glucose addition to 20% milk permeate solution on the process of formation of galac- tooligosaccharides during the enzymatic bioconversion of lactose by the examined beta-galactosidase preparations, was also studied. It was found that enzymatic synthesis of galactooligosaccharides in the process of lactose bioconversion was greatly dependent on beta-galactosidase used and that the presence of glucose in lactose solution already at the beginning of hydrolysis was favourable for the formation of oligosaccharides.